leveldb: Snapshot: add stringer
diff --git a/leveldb/db_snapshot.go b/leveldb/db_snapshot.go
index e41dcc6..0372848 100644
--- a/leveldb/db_snapshot.go
+++ b/leveldb/db_snapshot.go
@@ -8,6 +8,7 @@
 
 import (
 	"container/list"
+	"fmt"
 	"runtime"
 	"sync"
 	"sync/atomic"
@@ -89,6 +90,10 @@
 	return snap
 }
 
+func (snap *Snapshot) String() string {
+	return fmt.Sprintf("leveldb.Snapshot{%d}", snap.elem.seq)
+}
+
 // Get gets the value for the given key. It returns ErrNotFound if
 // the DB does not contains the key.
 //